1. Field of the Invention
The present invention relates to a wide angle picture-taking lens which is extremely compact and suitable for a lens shutter camera and the like.
2. Related Background Art
As a conventional picture-taking lens for use in a lens shutter camera, a behind stop triplet lens and a behind stop Tessar-type lens are well known. Since a lens system of these lenses is compact and composed of a small number of component lenses, three to four, imaging performance thereof is high and it is easy to attach a rear converter at the rear thereof. The lenses are therefore widely used at present.
In recent years, the demand for a wider angle of view has been also increased in the lens shutter camera.
Upon considering the demand, it is not possible to miss a latent demand for a compact camera in addition to a demand for what is called a wide angle photography.
In other words, if lenses which are the same in telephoto ratio (total length of lens/focal length) and different in angle of view are compared with each other, the lense which has the wider angle of view can have the shorter focal length with respect to the same picture size. Therefore, even if the lenses have the same telephoto ratio, the lens having the wider angle of view can be made more compact when being actually incorporated into a camera.
In short, it is possible to realize a wide angle lens and a compact camera.
However, the angle of view of the above triplet or Tessar lense is at most 65.degree. and it is difficult to say that the angle of the lense is sufficiently wide.
On the other hand, as a typical wide angle lens, what is called a Biogon-type lens and a retrofocus type lens for a single-lens reflex camera are well known.
However, since the structure of these lenses is complicated and large, and it is likely that the wider the angle of the lens, the larger will be the lens system thereof, these lenses are not suitable as a lens for a lens shutter camera which is required to be compact. Furthermore, it is difficult to attach a rear converter lens to achieve multiple focuses thereon.